1. Field of the Invention
The present invention relates to a method and installation for rehabilitating a ballast bed of a track.
2. Description of the Prior Art
EP 0 681 062 B1 and EP 0 790 352 A2 (corresponding to U.S. Pat. No. 5,479,725 reissued as Re. 35,788) discloses a method and installation for rehabilitating a ballast bed of a track, in which a first ballast excavating device preceding a second ballast excavating device excavates an upper ballast layer and conveys the excavated upper ballast layer to a screening unit for cleaning so that the cleaned ballast may be returned to the ballast bed. The remainder of the heavily contaminated ballast underneath the upper ballast layer is excavated by the second ballast excavating device and is temporarily stored in a storage hopper for disposal. The exposed subgrade is then improved by forming a protective layer over it.
U.S. Pat. No. 6,637,133 discloses a ballast cleaning machine designed to enhance efficiency with the use of two ballast cleaning devices operating in unison, the ballast excavated by both excavating devices being conveyed to a screening unit for cleaning. Such an arrangement requires a highly efficient screening unit.